Long seatpost for BSO?

One of my co-workers was inspired by my daily bike commute and bought himself a bicycle to ride to work on. Unfortunately, he got a "great deal" on a cheap, "Honda Racing" full suspension mountain-bike-style Bike Shaped Object. Worse, he bought a child's model with 24" wheels. The bike is way too small for him.

I'm trying to make this bike ridable, but I think it's a lost cause. I'd like to get a long seatpost and handlebar stem so at least he won't ruin his knees. The long seatposts that are available, however, won't fit his seat tube -- he needs something narrower.

Any suggestions on how to get a long seat tube for a retail store bike? This is a great illustration of why you shouldn't buy a bike from somebody who doesn't know bikes, but my co-worker wants to make this work.

Unless he's a really short guy, I think he's wasting his time (and probably even if he is).However, I do use an old folding bike that I extended the seattube on by using two seatposts, an angle grinder, three seatpost clamps, and a length of seattube from another scrap bike.It's not a great solution, but it works for me and it was a lot cheaper then buying an expensive new folder (and cheaper new folders I tried had too short seatposts (I'm 6'3")).(Dahon sensibly make long seatposts wider than standard short ones, so that's unlikely to be an answer.)

I'd encourage him to return it to get his money back. There's really no point. Likely, he's attracted to the low price. There are alternatives to cheap, department store bikes. Go to the Bike Kitchen in SF and make him a bike for $30.http://bikekitchen.org/